The present invention relates to cystic fibrosis transmembrane regulator (CFTR) mRNA compositions, uses of same, and methods of making and using same.
Cystic fibrosis is an autosomal inherited disorder resulting from mutation of the CFTR gene, which encodes a chloride ion channel believed to be involved in regulation of multiple other ion channels and transport systems in epithelial cells. Loss of function of CFTR results in chronic lung disease, aberrant mucus production, and dramatically reduced life expectancy. See generally Rowe et al., New Engl. J. Med. 352, 1992-2001 (2005).
Despite cloning of the CFTR gene in 1989, effective therapy for replacing CFTR for the treatment of cystic fibrosis has yet to be developed. The literature has documented numerous difficulties encountered in attempting to induce expression of CFTR in the lung. For example, viral vectors comprising CFTR DNA triggered immune responses and CF symptoms persisted after administration. Conese et al., J. Cyst. Fibros. 10 Suppl 2, S114-28 (2011); Rosenecker et al., Curr. Opin. Mol. Ther. 8, 439-45 (2006). Non-viral delivery of DNA, including CFTR DNA, has also been reported to trigger immune responses. Alton et al., Lancet 353, 947-54 (1999); Rosenecker et al., J Gene Med. 5, 49-60 (2003). Furthermore, non-viral DNA vectors encounter the additional problem that the machinery of the nuclear pore complex does not ordinarily import DNA into the nucleus, where transcription would occur. Pearson, Nature 460, 164-69 (2009).
Another source of difficulties in inducing CFTR expression in the lung is the lung environment itself. Pulmonary surfactant has been reported to reduce transfection efficiency for cationic lipid transfer vehicles such as Lipofectamine (DOSPA:DOPE). Ernst et al., J. Gene Med. 1, 331-40 (1999).
Also, Rosenecker et al., 2003, supra, identified multiple inhibitory components present in the airway surface liquid which can interfere with either polymer-mediated or lipid-mediated transfection. Messenger RNA therapy has been proposed as a general approach for inducing expression of a therapeutic or replacement protein. The concept of introduction of messenger RNA (mRNA) as a means of protein production within a host has been reported previously (Yamamoto, A. et al. Eur. J. Pharm. 2009, 71, 484-489; Debus, H. et al. J. Control Rel. 2010, 148, 334-343). However, apparent lung-specific difficulties have been reported for mRNA delivery using certain lipoplexes formulations. For example, a comparison of in vitro and in vivo performance of lipoplexes carrying mRNA or DNA revealed that even though the mRNA composition gave higher expression in cultured cells, measurable expression was detected only with the DNA composition when administered intranasally to mouse lung. Andries et al., Mol. Pharmaceut. 9, 2136-45 (2012).
It should also be noted that CFTR is a relatively large gene relative to model or reporter genes such as firefly luciferase (FFL). Compare the lengths of the wild-type CFTR coding sequence (SEQ ID NO: 2) and the FFL coding sequence (SEQ ID NO: 7). The difference in length can impact stability under some circumstances, and therefore whether and how much protein expression any given dose of mRNA will produce. Furthermore, although in vitro synthesis of mRNA is generally preferable to synthesis by cells due to the absence of normal cellular mRNA and other cellular components which constitute undesirable contaminants, in vitro synthesis of mRNA with a long coding sequence, such as CFTR mRNA, is substantially more difficult to achieve than in vitro synthesis of mRNA with a relatively short coding sequence such as FFL.
PCT patent publication WO2007/024708 and US patent publications US2010/0203627 and US2011/0035819 discuss the therapeutic administration of CFTR mRNA but provide neither a demonstrated reduction to practice of production of functional CFTR in the lung following administration of CFTR mRNA or sufficient guidance for overcoming the difficulties associated with inducing CFTR expression in the lung using in vitro-transcribed CFTR mRNA. These include difficulties with achieving in vitro synthesis of the mRNA and difficulties specific to the interactions of mRNA compositions with lung-specific substances that investigators such as Andries et al., supra, have found to render mRNA compositions ineffective for induction of expression even while corresponding DNA-based compositions did provide some level of expression.
Thus, there is a need for improved materials, formulations, production methods, and methods for delivery of CFTR mRNA for induction of CFTR expression, including in the mammalian lung, for the treatment of cystic fibrosis.